1. Field of the Invention
The present invention relates, in general, to transit vehicle door systems and, more particularly, the instant invention relates to a rotary door operator and, yet more particularly, the instant invention relates to a rotary door operator having a “zero-lead” or a “lift-and-lock” locking feature.
2. Description of Related Art
Prior to the development of the present invention, as is generally well known in the art, a rotary door operator is mainly used in the inter-city bus coaches. These rotary operators are available in two distinct types, commonly referred to as zero-lead and lift-and-lock. Either door operator type can be adapted for use with pneumatic or hydraulic fluids.
The rotary door operator of the zero-lead type converts piston motion of a piston-power cylinder unit into a rotary motion by means of roller pairs engaging oblique slots with an axial direction at their ends. One of the cylinders within the piston-power cylinder unit is connected to the power output shaft which, in turn, is connected to a door of the vehicle. During the door closing cycle, the output shaft moves upwardly in the vertical direction. When the door reaches a closed position, the roller pairs disposed at the end of the axial portions provide rudimentary locking of the door providing that the piston-power cylinder unit is charged with fluid and that no leakage occurs.
The rotary door operator of the lift-and-lock type comprises a double acting drive cylinder driving an output shaft coupled to the door post. The output shaft has a splined shaft member connected to the drive cylinder through a helical ball cage in order to provide a rotary motion and engageable with the door post carrying the door. The output shaft also has an antirotational shaft member enabling vertical movement of the output shaft to lock and unlock the door. When the door reaches the closed position, the rotary door operator lifts the door post and, subsequently, the door connected to the door post by approximately 10 mm, enabling door mounted wedges to engage mating wedges mounted adjacent a portal aperture of the transit vehicle. In the opening direction the output shaft first moves in a downward direction disengaging the wedges and enabling rotation of the door post.
To close the transit vehicle door, the cylinder is charged with fluid pressure through the first orifice. The rate at which the door closes depends solely on the rate at which the cylinder is charged with fluid. The splined shaft member connected with a drive cylinder piston moves linearly in the upward direction while engaging an antirotational shaft member. Such upward motion of the output shaft causes rotation of the post in the first direction and, more particularly, causes the closing motion of the door.
To open the transit vehicle doors, the drive cylinder is charged with fluid pressure through the second orifice. The rate at which the door opens depends solely on the rate at which the cylinder is charged with air. The output shaft moves linearly in the downward direction and causes rotation of the splined shaft in the second direction to open the door.
Such lift-and-lock feature is the mechanism disposed within the door operator preventing the un-locking of the door. When such door contacts door jambs of the door portal aperture, the mounting linkage attached to the door at one end and attached to such door operator at the distal end stops rotating. Since the drive cylinder has not reached the end of the stroke, the output shaft continues to move upward lifting such door and enabling door locking wedges to substantially engage mating locking wedges disposed adjacent the portal aperture.
One of the main disadvantages of these designs is that loss of fluid pressure will cause downward movement of the door, thus disengaging such mating wedges in lift-and-lock applications or simply unlock the door in zero-lead applications and, more particularly, the loss of fluid pressure will create a hazardous condition due to an unlocked door.
To overcome the aforementioned concern associated with fluid pressure loss, lock mechanisms have been employed in such rotary door operators.
U.S. Pat. No. 4,545,149 to Jentsch teaches a lock mechanism for a lift-and-lock door operator type. Such lock mechanism employs a support member positioned under a disk that is permanently attached to the output shaft and an unlocking member, which engages such support to prevent its rotation in the unlocking direction. In the door locked position, the disk rests on the support member thus preventing downward movement of the output shaft. The support member incorporates adjustment means to maintain a contact with the disk. The unlocking member is connected to a unlock cylinder. To unlock the door in a normal operation, the unlock cylinder is energized causing rotation of the unlocking member which enables the support member to rotate in the unlocking direction and, more particularly, enables the output shaft to move downwardly and disengage the door wedges.
Manual unlocking of the door is achieved via Bowden cable that is attached to the unlocking member. In addition the Bowden cable is attached, through a plurality of linkages, to a fluid-evacuation valve which must be opened in order to evacuate fluid pressure from the unlock cylinder. Such Bowden cable is routed from the bottom of the rotary operator to rotate unlocking lever in the clockwise direction to unlock the door.
There are several disadvantages related to this type of lock mechanism. In the first aspect, the disk rests on the support member creating a frictional force that must be overcome during door unlocking movement. In the second aspect, the engagement between support member and the unlocking member, as best understood, creates an additional frictional force. As it is well known in the art, frictional forces cause premature wear and reduce reliability of the design. In the third aspect, manual unlocking of the door incorporates additional linkage to open a fluid pressure evacuation valve which further increases the complexity of the design. In the fourth aspect, the Bowden cable must be routed from the bottom portion of the door in order to enable clockwise rotation of the unlocking lever.
U.S. Pat. No. 4,854,223 to Fink teaches a lock mechanism for zero-lead rotary door operator. Such lock mechanism utilizes a blocking lever to block downward movement of the roller pair only when fluid pressure loss occurs. The blocking lever is connected to the spring loaded rod of the lock cylinder. In normal operation, the lock cylinder is charged at all times to maintain the blocking lever in the unlock position additionally compressing its internally mounted spring.
Manual unlocking of the door is achieved via Bowden cable connected to the blocking lever at one end and connected to a lever at a distal end. The lever is employed to activate a three-way valve in order to remove the fluid pressure from the line and open the door via the Bowden cable. The Bowden cable is also routed from the bottom portion of the door in order to provide a desired rotation of the blocking lever. As best understood, the three-way valve is mounted remotely from the rotary door operator.
As it is well known in the art, routing of the Bowden type cable, typically incorporated into a structure of the transit vehicle, requires special mounting and guiding considerations so not to provide for possibility of cable damage and at the same time assure proper cable operation. Of a particular concern is a guiding and mounting of the cable in a close proximity near its end engageable with the locking/unlocking levers. As best understood, the prior art designs do not provide for such guiding and mounting means integral to the rotary door operator.
As it can be seen from the above discussion there is a need for a relatively simple, reliable and versatile manual unlock mechanism for a rotary door operator.